Help me diagnose an issue with my new Blue Angel.

[escher]

Just picked up a mint condition Blue angel tonight - and I love it, but I heard some strange noise when its right on the edge of breakup. So I did some research and swapped the reamp tubes and the el84's, but no change.

It occurs on all power tube settings - 6L6, EL84 and mixed.

Maybe the rectifier???

Soundclip:

http://www.izak-custom.com/Music/blue-angel-issue.mp3

Have a listen and let me know if you recognize the issue - I literally just picked this up from a guy about an hour away... man I hope I don't have to start saving up to ship it to Mesa...

Can anyone help?

Thanks!

 

[94Tremoverb]

It doesn't actually sound like tubes to me, but it's worth being sure - first, you need to eliminate the power tubes.

Actually remove the unused ones, not just switch them off - they remain in the circuit and are only disconnected at the cathodes, so some types of short can still cause trouble. Pull all four EL84s and set the amp to 6V6, and test. Then repeat with the EL84s back in and the 6V6s out, set to EL84.

(It is OK to use 6L6s instead of 6V6s if that's what you meant to say, by the way.)

If that doesn't locate it, remove V3 which is the reverb driver - a short in this can sometimes feed back into the signal path. (If you need to replace this one, I found that a 12AT7 sounded much better than the stock 12AX7 here.)

You could also try - if you have a pedal or other preamp with enough output level - running the guitar into the FX return (set the Mix to 100%), bypassing the preamp altogether. This would tell you if the problem is in the preamp or the power stage.

 

[escher]

Thanks for the advice - I'll definitely be digging into it when I get home tonight. And yes - I meant to say 6V6 - my bad...


I did have another issue after I had swapped tube last night - As I was playing, if I drove it at all, i.e. with the volume or using a pedal to up the signal, after a couple of minutes, the output would slowly drop to nothing. After a couple of minutes it would come back on, and then repeat.

It was as if the amp has a over heat or overload protection circuit that was kicking on...

Any ideas?

I didn't notice it doing this before the tube swap - so I'm going to go back the the original tubes tonight and test again - wondering if its a flaky preamp tube that is heating up and shorting out or something...

I'm going to give Mesa a call today as well to get their input...

 

[escher]

Well Its definately in the power section.

I replaced the rectifier - and that fixed the power loss issue. But the buzzing issue remains.

I took your advice and bypassed the preamp section by going direc into the effects loop - and the buzz was still there on all power tube settings.

Looks like a trip into the amp tech is in order. Probably a loose solder joint or something.